Celiac disease is the most common genetic disease in Europe. In Italy, about 1 in 250 people and in Ireland, 1 in about 300 people has celiac disease. It is rarely diagnosed in African, Chinese and Japanese people.

An estimated 1 in 4,700 Americans have been diagnosed with celiac disease. Some researchers question how celiac disease could be so uncommon in the United States since it is hereditary and many Americans descend form European ethnic groups in whom the disease is common. A recent study in which random blood samples from the Red Cross were tested for celiac disease suggests that as a many as 1 in every 250 Americans may have it. Celiac disease could be under diagnosed in the United States for a number of reasons: